1. Field of the Invention
The present invention concerns a friction clutch, in particular for motor vehicles, and more particularly a clutch provided with a device for compensating wear due in particular to wear of the friction linings, said device, referred to hereinafter as a wear compensator device, operating as and when said linings wear.
2. Description of Related Art
A conventional friction clutch generally includes a reaction plate, possibly in two parts to form a damper flywheel, constrained to rotate with a first shaft, usually a driving shaft such as the crankshaft of the internal combustion engine, its outside periphery supporting a cover to which at least one pressure plate is attached.
The pressure plate is constrained to rotate with the cover and the reaction plate but can be moved axially by axially acting clutch engaging means operated by clutch release means; the clutch engaging means can be coil springs or two Belleville washers disposed in series and acted on by clutch release levers forming the clutch release means; the clutch engaging and clutch release means are generally part of the same component, for example a metal diaphragm bearing on the cover; the diaphragm can be disposed in series as described in document FR-A-2 753 758 or in parallel with a Belleville washer to assist the clutch release force.
A friction disc carrying friction linings at its outside periphery and constrained to rotate with a shaft, usually a driven shaft such as the input shaft of the gearbox, is disposed between the pressure plate and the reaction plate so that it is clamped between them when the clutch is in the engaged position. The clutch engaging means move the pressure plate axially when they are actuated by a clutch release thrust bearing through the intermediary of the clutch release means.
During the service life of a clutch of the above kind the friction linings and the materials on which they bear on the pressure plate and the reaction plate wear away, which varies the position of the pressure plate and the positions of the axial action clutch engaging means and the clutch release thrust bearing, which in turn varies the clamping force between the friction disc and the pressure and reaction plates because of modifications to the working conditions of the clutch release means, and this affects the force needed to release the clutch. Providing a clutch of the above kind with a wear compensator device avoids the above drawbacks because the clutch engaging means and the clutch release thrust bearing, usually bearing at all times on the clutch release means, occupy the same position when the clutch is in the engaged position.
If a clutch is provided with a wear compensator device it is beneficial, after it has exercised its function, to return it to a position corresponding to new friction linings, for example after changing the friction disc because its linings have been worn down; this also facilitates placing the clutch in a storage configuration.